1. Field of the Invention
The present invention relates generally to medical devices and methods for their fabrication. In particular, the present invention relates to the fabrication of biodegradable endoprostheses, such as stents, having enhanced strength and controlled persistence after implantation.
Stents are generally tubular-shaped devices which function to hold open or reinforce a segment of a blood vessel or other body lumen, such as a coronary artery, carotid artery, saphenous vein graft, or femoral artery. They also are suitable to support and hold back a dissected arterial lining that could occlude the body lumen, to stabilize plaque, or to support bioprosthetic valves. Stents can be formed from various materials, particularly polymeric and/or metallic materials, and may be non-degradable, biodegradable, or be formed from both degradable and non-degradable components. Stents are typically delivered to the target area within the body lumen using a catheter. With balloon-expandable stents, the stent is mounted to a balloon catheter, navigated to the appropriate area, and the stent is expanded by inflating the balloon. A self-expanding stent is delivered to the target area and released, expanding to the required diameter to treat the disease. Stents may also elute various drugs and pharmacological agents.
Of particular interest to the present invention, biodegradable stents and other endoprostheses are usually formed from polymers which degrade by hydrolysis and other reaction mechanisms in the vascular or other luminal environment over time.
For these reasons, it would be desirable to provide improved endoprostheses and methods for their fabrication.
2. Description of the Background Art
Heat annealing and other treatments of filaments and other components used in stents are described in U.S. Pat. Nos. 5,980,564, 6,245,103, and 6,626,939. Heat treatment of polymeric stent coatings is described in International Application No. PCT/US07/81996, which designates the United States.
Biodegradable implantable devices and methods of making them are also described in commonly owned U.S. Provisional Patent Application No. 60/668,707, filed on Apr. 5, 2005; U.S. Provisional Patent Application No. 60/885,700, filed on Jan. 19, 2007; U.S. patent application Ser. No. 11/398,363, filed on Apr. 4, 2006; U.S. patent application Ser. No. 12/016,077, filed on Jan. 17, 2008; and U.S. patent application Ser. No. 12/016,085, filed on Jan. 17, 2008, the entire disclosure of each of which is incorporated herein by reference.